1. Field of the Invention
The field of the invention is that of locks having multiple levels of keys such that some keys may open more locks than other keys.
2. Prior Art
It has been a problem with some multiple level key systems that higher level keys may be produced from lower level keys by removing lateral profile ribs on the lower level or subordinate keys. This technique works in installations where the higher level keys are distinguished by means of diminishing numbers of profile ribs compared with lower level keys. In order to prevent a key with a filed-away rib from being used as a higher level key, a profile lock in accordance with German Pat. No. 15 53 529 may be used. This lock consists of one or more laterally scanning locking pins which are positioned in bores of the rotary cylinder and are positioned with their outer edges corresponding to the perimeter of the rotary cylinder only when the key profile currently inserted in the lock has the predetermined size. If this profile width is reduced or completely lacking, then the locking pins are displaced a lesser amount and an obstruction of the lock occurs whereby after beginning to rotate the cylinder core, the spring-biased housing pin corresponding to that pair of scanning pins will drop into the bore occupied by one of the scanning pins which has been left partially opened due to the imperfect position of the scanning pins.
There has been a need for a simple though more secure means of safeguarding against unauthorized production of high level keys from subordinate keys.